1. Field of the Invention
The present invention relates to a method of and apparatus for measuring mercury contained in a hydrocarbon such as, for example, naphtha and LPG (liquefied petroleum gas).
2. Description of the Prior Art
It has been well known in the art that hydrocarbons such as, for example, naphtha, contain mercury, particularly dimethylmercury. It is also well known that various components of mercury are responsible for the degradation of the capacity of a catalyst such as paradigm or platinum employed for producing various kinds of petrochemical products from naphtha. For this reason, countermeasures have been considered necessary to measure the amount of mercury contained in hydrocarbon and to remove the mercury when the amount of mercury contained in the hydrocarbon exceeds a predetermined value.
Hitherto, attempts for mercury measurement have been made to use a heated vapor analyzing device including a sample port in which a sample comprising hydrocarbon is directly injected. With this heated vapor analyzing device, mercury contained in the sample is measured after having been vaporized by heating the sample port within a combustion tube. Also, during the measurement, additives are added together with the sample to remove interfering gases that are generated from the sample and are likely to disturb the mercury measurement.
However, with the conventional method of measuring mercury discussed above, it has been experienced that when mercury contained in the sample is vaporized by heating, hydrocarbon is simultaneously volatized from the sample to produce an inflammable gas. Accordingly, in order to avoid a rapid generation of the inflammable gas, stringent measurement conditions are required as to the quantity, type and flow rate of the sample and also as to the temperature rise rate of the sample and so on. Also, similarly stringent requirements are imposed on selection of the additives.
In view of the foregoing, the present invention is intended to provide a method of and an apparatus for measuring mercury, which are effective to measure mercury easily with the above discussed stringent measurement conditions being alleviated.
In order to accomplish the foregoing object of the present invention, there is, in accordance with one aspect of the present invention, provided a method of measuring mercury that is carried out by causing a mercury-free gas, i.e., a gas containing no mercury, to flow through a column filled with an adsorbent material effective to adsorb mercury. While the mercury-free gas flows through the adsorbent containing column, the hydrocarbon to be measured is injected to allow mercury, contained in the hydrocarbon, to be adsorbed by the adsorbent material to thereby remove a volatile component other than mercury, followed by measurement of the mercury with the use of a mercury measuring instrument.
In the practice of the foregoing embodiment of the mercury measuring method of the present invention, while the mercury-free gas flows through the column, hydrocarbon to be measured is injected into the column and mercury contained in the hydrocarbon is then adsorbed by the adsorbent material within the column. The hydrocarbon from which the mercury is thus removed is subsequently discharged to the outside together with the gas and is removed out of the column. The column is thereafter inserted in the mercury measuring instrument so that the mercury adsorbed by the adsorbent material within the column is heated to vaporize and is then measured.
During the measurement, even though the mercury is heated to vaporize, no inflammable gas is generated since the hydrocarbon has already been removed from the column. Also, since only the carrier air containing no mercury, that is, the mercury-free carrier air which flows through the column, and mercury adsorbed by the adsorbent material are present within the column and no interfering gas such as hydrocarbon which would otherwise interfere with measurement of the mercury is present within the column, the present invention is effective to dispense with the use of any additives hitherto required to remove the interfering gas. Because of this, the present invention makes it possible to perform the mercury measurement easily without requiring such stringent measurement conditions as hitherto required. Yet, in contrast to the prior art in which for the purpose of securing a safety the maximum amount of hydrocarbon that can be measured at a time is limited to 100 xcexcL, the present invention allows an increased amount of hydrocarbon, say, 200 xcexcL or more, to be measured at a time and, therefore, the mercury contained in the hydrocarbon can be accurately measured.
In a different embodiment of the mercury measuring method of the present invention, a feature thereof resides in that organic mercury and metallic mercury contained in hydrocarbon are measured by differentiatedly collecting them. More specifically, the present invention also provides a method of measuring organic mercury and metallic mercury contained in hydrocarbon by differentiatedly collecting the organic mercury and the metallic mercury, which is carried out by preparing first column, filled with a first absorbent material effective to adsorb organic mercury, and a second column fluid-connected in series with the first column and filled with a second adsorbent material effective to adsorb metallic mercury; injecting hydrocarbon to be measured into the first column while a gas containing no mercury is allowed to flow through the first and second columns sequentially; heating the first column to transform the metallic mercury contained in the hydrocarbon into a gaseous fluid so as to flow through the first adsorbent material and also as to cause the organic mercury to be adsorbed by the first adsorbent material; causing the second adsorbent material within the second column to adsorb the metallic mercury; and measuring the organic mercury and the metallic mercury, which have been differentiatedly collected by the first and second columns, respectively, by means of a mercury measuring instrument.
In the practice of the mercury measuring method according to the different embodiment of the present invention, while the mercury-free gas flows through the first and second columns, hydrocarbon to be measured is injected into the first column. Since the first column is heated, metallic mercury contained in the hydrocarbon is gasified and flows through the first adsorbent material within the first column, while only organic mercury contained therein is allowed to be adsorbed by the first adsorbent material. The gasified metallic mercury is fed to the second column together with the mercury-free gas and the gaseous metallic mercury is subsequently adsorbed by the second adsorbent material within the second column. The hydrocarbon from which the organic and metallic mercury is thus removed is subsequently discharged to the outside together with the gas and is removed out of the first and second columns. The first and second columns are thereafter inserted in the mercury measuring instrument so that the organic and metallic mercury adsorbed differentiatedly collected by the first and second adsorbent materials within the first and second columns, respectively, are heated to vaporize and are then measured.
At this time, as is the case with the mercury measuring method according to the previously described embodiment of the present invention, even though the organic and metallic mercury is heated to vaporize, no inflammable gas is generated since the hydrocarbon has already been removed from the first and second columns. Also, since no interfering gas which would otherwise interfere with measurement of the mercury is present within the first and second columns, the present invention is effective to dispense with the use of any additives hitherto required to remove the interfering gas. Because of this, the present invention makes it possible to perform the mercury measurement easily without requiring such stringent measurement conditions as hitherto required.
In the practice of any of the foregoing mercury measuring methods, the mercury-free gas may be air.
In another aspect of the present invention, there is provided a mercury measuring apparatus designed to perform the first mentioned embodiment of the mercury measuring method. This mercury measuring apparatus includes a column filled with an adsorbent material effective to adsorb mercury in hydrocarbon; a pump for flowing through the column a gas containing no mercury; an injector for injecting hydrocarbon to be measured into the column while the gas flows through the column; and a mercury measuring instrument for measuring mercury which has been adsorbed by the adsorbent material.
There is also provided a mercury measuring apparatus designed to perform the second mentioned embodiment of the mercury measuring method. This mercury measuring apparatus includes a first column, filled with a first adsorbent material effective to adsorb organic mercury; a heater for heating the first column so as to allow a gaseous metallic mercury, contained in the hydrocarbon, to flow through the first adsorbent material; a second column connected in series with the first column and filled with a second adsorbent material effective to adsorb metallic mercury; a pump for flowing a gas, containing no mercury, through the first and second columns sequentially; an injector for injecting the hydrocarbon to be measured into the first column while the gas containing no mercury flows therethrough; and a mercury measuring instrument for measuring the organic mercury and the metallic mercury which have been differentiatedly collected by the first and second columns, respectively.
The injector referred to above may be a micro-syringe. Also, the gas containing no mercury may be air, in which case the pump is disposed downstream of the column with respect to a direction of flow and a mercury removal filter is preferably disposed upstream of the column for removing mercury from air to achieve a mercury-free flow through the column.